The overall objective of the current SCOR and the Proposed Renewal is to elucidate the molecular basis for the long-term adaptive response of the heart to injury, both inherited and acquired, where manifested by hypertrophy or dilitation. This proposal encompasses 5 collaborative investigations, supported by integrated core facilities to address issues fundamental to the etiology, pathogenesis and treatment of cardiac failure. Novel genes will be identified responsible for inherited cardiac disorders, familial dilated cardiomyopathy (FDCM) manifested in the left ventricle and arryhthmogenic right ventricular dysplasia in the right ventricle, as paradigms of dilated cardiomyopathy, the most common form of acquired heart failure. To date, two genes (cytoskeletal) have been identified that cause DCM, actin and desmin. Thus, cytoskeletal proteins may provide a unifying causality for DCM analogous to that of sarcomeric proteins for HCM. Accordingly, insight gained from expression of the mutant desmin in the transgenic mouse should have pathogenetic implications for DCM due to other defective cytoskeletal proteins, whether familial or acquired. While assembly and organization of the cytoskeletal components are an integral part of the cardiac growth response, their role as heretofore been ignored until the identification of the integrin signaling pathway (RhoA, Focal Adhesion Kinase, and Integrin Linked Kinase). In Dr. Schwartz' project, dominant negative mutants of these molecules will be used in cardiac myocytes and Gene-Switch transgenics to determine whether one or all of these are necessary for cytoskeletal assembly and hypertrophy. FHCM, due to over 100 mutations in seven genes, develops the secondary phenotype of increased fibrosis and hypertrophy, providing the opportunity for prevention. Renin-angiotensin system (RAS) inhibitors will be assessed in transgenics harboring the human cTNT mutation and, in preparation for future gene therapy, Gene-Switch will be used to determine if the phenotype is reversible. Growth factor(s) responsible for the secondary phenotype will be sought through subtraction hybridization. A novel pathway (TNFalpha) shown in the current SCOR to play a pivotal role in the growth response (hypertrophy) and heart failure (apoptosis), will be pursued to identify molecular interaction with RAS, both in genetic models and in patients with heart failure and to develop novel specific therapies. Strategies to achieve the aims, will utilize "state of the art" techniques: automated genetic analyzers for genotyping and DNA sequencing, BACs, YACs, and DNA microchip arrays to identify genes, the RU-486 Gene Switch to regulate expression of transgenes, PCR-generated dominant negative mutants, "gutless" tetracycline dependent adenoviral vectors, selective elimination of genes (knock-out mice), and Ta178 radionuclide angiography to assess mouse cardiac function. These studies elucidate further the molecular foundations of cardiac hypertrophy and failure and should provide a rational basis for more effective therapy.